Ive got a question about the flex fuel, i haee a 2009 HHR with the 2.2, it started running rough, idling like crap, had now power, was missing, tried everything and could not figure it out, took it to the dealer and they said body control module was bad, replaced that and still not running right, they then refused to work on it after having it for almost 8 months, long story short brought it home and my neighbor builds race engines for dirt drag trucks and has HP tuners, he said bring it over will will look at it, after he scanned it and looking at ALL variables he noticed that it was showing to have 100% alcohol in the fuel, HP tuners had an option to turn off flex fuel so we did and it ran fine for about a week. Im still running it now but the check engine light is back on and it shows a P0420, P0442, P0455, it has brand new Bosch O2 sensors, both of them,, put a new purge tank under it by the gas tank about 3 years ago. I saw in this post that someone said there is no flex fuel sensor on this car. I am leaning toward the cat converter is gong out, but other than not getting the best fuel efficiency it runs ok. Any ideas guys??

 

P0420 usually indicates the cat is damaged.

P0442 indicates the under hood purge valve is defective , check to see if you can blow air through it, it should be closed.

P0455 indicates a large leak, start by inspecting the seal at the new purge tank, most replacements do not include the seal and the OEM seal gets tossed.

Welcome to the forum!

 

The CEL is "still on"? Meaning no one bothered to scan for codes? P0420 means the problem is a clogged cat.
The HPTuner should have a way to just reset the alcohol.

Bosch O2 sensors are notoriously bad.

I don't understand: first you say "t started running rough, idling like crap, had now power, was missing" Then say " but other than not getting the best fuel efficiency it runs ok".
I never heard of a GM shop refusing to take money. Why did it sit on their lot for 8 months?

 

Welcome to the forum.
The dealer replaced the BCM ? That’s the Body Control Module. That is the module/ fuse box in the interior. Not really related to any engine controls or module. Sounds like the dealer didn’t have a clue.
Now if they would have suspected the ECM, I could believe that.

 

HP tuners option to “turn off flex fuel” (whatever that means) was not the best move in this case. Some (many?) GM FlexFuel cars, for unknown reasons (except possibly to GM,) sometimes get confused about the ethanol content in the tank. This is an obvious problem in your case, as evidenced by the 100% setting.

I won’t go into all the explanations for this (yet?) but there is at least one TSB about this problem, addressing in on multiple vehicles, and not just Ecotecs. I’ve covered this in other threads in these forms.

As advised in the TSB, the better thing to do is to set the stored alcohol content to zero (assuming you have regular in the tank and not E 85.) Clearing codes or disconnecting the battery does not affect the stored ethanol content.

Some code readers won’t can’t read the stored ethanol content. Others will read it, but can’t reset it. It usually takes a fairly robust scan tool to reset it.

You will find advice everywhere advising to not use Bosch O2 sensors, as Don mentioned.

 

I had a time even finding a GM dealer that would work on it, i took it to several dealers in my area and they refused saying its too old they do not work on anything that old, finally the one did, and they just could not figure it out, then got bought out by another group, changed a lot of mechanics and then ultimately got tired of working on it and refused to go further, i had to push it on a trailer to get it home from the dealer, it wasn't until we cut the flex fuel off with HP tuners program that it started running better, it ran great for one week or so and still does. its just I'm not getting top fuel economy, i use to average 29-30 a gallon, now I'm getting 25-26 on average and the check engine light shows the aforementioned codes.

 

From what i remember there was not an option to reset the alcohol content to zero in HP tuners and i do not have access to a scan tool to do that, ill have to try to see if i can get that done.

 

First I have heard of any shop turning away business, usually the opposite ; overcharging and throwing parts at it.
So, nobody ever bothered to read the codes before? Everybody think the CEL is just a pretty light?
The reason for poor MPG is that the computer is in open loop mode, not using the sensors for input, and the cat is clogged unless the HPTuner thing did something like turning the sensors off
The computer calculates the Alcohol content based on input from the O2 sensors, not a specific alcohol sensor.

 

Dealers are mostly clueless on this issue. I had my dealer do the reset but I had to tell them exactly what to do. The good news was they had the decency to simply follow instructions, and charged me only $65 half a hour, and didn’t try to charge me for a diagnosis. I have been very pleased with this dealer’s service department. This is the exception, not the rule.

One of these days I’m gonna get a decent scan tool.

BTW, the way, you were really lucky to discover the improbable stored alcohol percentage early. in the past I’ve had trouble convincing owners here to even check it. One guy replaced half the car before finally figuring out that it was an incorrect alcohol %.

My free Torque app reads it, won’t reset it.

One workaround is to simply fill the car with E85, but because the actual % from the pump is anywhere from 51-83%, that may not suffice with your 100% value.

Also, sometime the car will gradually correct itself.

Some conditions associated with the erroneous alcohol %:
Frequent very short trips.
Fuel/evap system leaks
Other fuel/emission system malfunctions*
Onset of cold weather
Recent refueling, especially with funky fuel
Failing to turn off the car when refueling
”Topping off” when refueling

*As Old Blue, said there is no ethanol sensor and the car uses other metrics to estimate the ethanol content in the fuel. Therefore, the entire fuel emission system needs to be functioning properly, especially the cat and O2 sensor. But I think a dirty MAF sensor, or throttle body, or fuel injectors, or even misfire caused by compression or ignition problems could contribute.

The car is triggered to recalculate the % after detecting a refueling event. A increase of minimum of something like 3 gallons is needed.

 

Then you concur the Bosch O2 sensors and catalytic converter could cause the alcohol content issues .
And to clarify, Donbrew pointed out that there isn’t a specific sensor for alcohol content